Pressure vessels or other fluid-bounding enclosures can be found in a great variety of shapes, sizes, and materials to suit specific requirements including environmental conditions, serviceability, functionality, manufacturability, and other pertinent requirements. In one permutation these vessels can be standalone sealed enclosures for use in immersed ambient fluid environments such as seawater. Often such enclosures contain heat generating components such as power electronics which operate at a nominal temperature exceeding that of the ambient fluid. It is often desired to transfer the heat to the ambient fluid environment. The heat generating components are typically fastened mechanically to allow for thermal conduction through the vessel wall to the ambient fluid. For passive heat transfer these types of enclosures have traditionally relied upon direct contact between the enclosure wall and the ambient fluid to setup a thermal energy transfer by convection. In high heat flux applications extended fin surfaces on the enclosure wall are a common method to improve passive heat transfer performance. For active heat transfer systems, pumps, fans, and other powered devices assist in the heat transfer (e.g. car engine cooling system).
Remotely Operated Vehicles (ROVs) are an example of an underwater system which commonly includes pressure vessels which generate significant amounts of heat such as motor controllers, hydraulic power units, and power transformers. Typically, flotation foam is used in the upper volume of the vehicle for stability, but also in interstitial areas between components (cameras, lights, thrusters, pressure vessels, structure, etc.) for highly efficient (e.g. power, size, displacement, etc.) vehicle systems. For these complex vehicle systems, compromises are often made to achieve performance goals for speed, hydrodynamics, power efficiency, stability, buoyancy, and other factors. In these systems, pressure vessel design and flotation design may be compromised to meet opposing requirements for heat dissipation and vehicle performance. Typically, any heat generating components are located to allow maximum water flow to aid in heat transfer, but this may increase hydrodynamic drag of the vehicle leading to negative system performance. A specific instance of this may entail a motor controller pressure vessel problematically located on the ROV in order to permit heat transfer from the vessel wall to the surrounding seawater.